Degree of Saturation and Free Fatty Acid Content of Fats Determine Dietary Preferences in Laying Hens

Abstract

Behavioural and genetic evidence shows that the taste system is intimately related to the sensing of nutrients with consequences for poultry nutrition practices. A better understanding of how chickens may sense fat could provide the background for selecting feedstuffs used in poultry feeds. Acid oils have the potential to be economical and sustainable feedstuffs. These fat by-products from the edible oil refining industry possess a similar fatty acid composition to the crude oils but are richer in free fatty acids (FFA). An experiment was conducted to study the effect of FFA content and the unsaturated:saturated ratio (U:S) on dietary preferences in hens. Four fat sources were added to a basal diet at an inclusion rate of 6%, determining the experimental diets: soybean oil (SO; high U:S, 5% FFA); soybean acid oil (SA; high U:S, 50% FFA); palm oil (PO; low U:S, 5% FFA); and palm fatty acid distillate (PFAD; low U:S, 50% FFA). The experimental diets were offered in a series of double-choice tests to forty-eight Lohmann Brown laying hens housed individually in cages. Each hen was offered the ten potential binary combinations of the four diets including each diet compared to itself (referred to as four control double-choices). Feed intake was measured for two hours twice a day after one hour of fasting. Consumption was analysed as a standard preference index (% of test diet intake in comparison with the total intake). Preference values were compared to the random choice value of 50% using the Student’s t-test. None of the four control comparisons differ significantly from 50% (p > 0.05), indicating that the changes in preference values observed in the other binary comparisons were related to the dietary changes associated to fat ingredients. Hens showed a feed preference for palm oil added diets over soybean oil diets (p < 0.05), with PO and PFAD being equally preferred (p < 0.05). However, in this trial the hens demonstrated a preference for SO (low %FFA) when offered in choice with SA (high %FFA) (p < 0.05). These results suggest that the degree of saturation plays an important role in dietary fat preferences: hens prefer predominantly saturated oils even when these are rich in FFA. Furthermore, when presented with a choice between predominantly unsaturated oils, hens prefer feed with a low %FFA. In conclusion, %FFA and the U:S ratio affected feed preferences in hens. The use of oils with greater preference values may give rise to greater feed palatability, enhancing feed intake at critical stages.

Influence of free fatty acid content and degree of fat saturation in laying hen diets on egg quality, yolk fatty acid profile, and cholesterol content

“…Fats and oils have the highest caloric values among all the ingredients used in poultry diets. Adding supplemental dietary fat also confers other benefits, including providing essential fatty acids ( FA ), such as linoleic acid ( LA ), and fat-soluble vitamins, while also improving palatability, and allowing better nutrient digestion and absorption ( Mateos and Sell, 1981 ; Grobas et al, 1999b ; Bouvarel et al, 2010 ; Ravindran et al, 2016 ; Palomar et al, 2020 ).…”

The avian taste system

“…Different fat sources at inclusion rate of 6% with different amounts of free FA and various level of unsaturated to saturated FA ratios were added to laying hens' diet. Results showed a higher preference for higher free FA and a stronger preference for saturated than unsaturated FA (Palomar et al, 2020). In addition, chickens did not show significant preferences for oleic acid (a mono-unsaturated FA) in choice feeding tests (Kawabata et al, 2021).…”

“…Similar to the calcium oral sensing, it is also speculative to define a sense of fatty taste in birds based on only indirect evidence such as choice feeding tests and the existence of the fatty acid (FA) receptors in the oral cavity. Behavioral studies regarding FA sensing in chickens have consistently shown preferences for long-chain FAsupplemented feeds (Furuse et al, 1996;Mabayo et al, 1996; Frontiers in Physiology frontiersin.org Vermaut et al, 1997;Palomar et al, 2020). Different fat sources at inclusion rate of 6% with different amounts of free FA and various level of unsaturated to saturated FA ratios were added to laying hens' diet.…”

Influence of free fatty acid content and degree of fat saturation on production performance, nutrient digestibility, and intestinal morphology of laying hens

“…(2021) compared soybean and palm diets with different FFA content and reported higher BW in grower-finisher broilers (37 days) fed soybean diets, and Jimenez-Moya et al., 2021a , Jimenez-Moya et al., 2021b found no differences in broilers fed diets with different UFA:SFA ratios and FFA content. Differences in feed intake could be attributed to differences in the AME values, although it is also noteworthy that an earlier palatability study found that hens preferred SFA-rich oils over UFA-rich oils even when they were also rich in FFA ( Palomar et al., 2020 ).…”